Cri du chat syndrome – causes, symptoms, diagnosis, treatment, pathology

Cri du chat syndrome – causes, symptoms, diagnosis, treatment, pathology


Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
a personalized study plan with exclusive videos, practice questions and flashcards, and so
much more. Try it free today! Cri du chat syndrome is a rare genetic disorder
caused by a genetic mutation where a portion of chromosome 5 is deleted, or missing. The name is a french term that refers to the
characteristic high-pitched cry of the affected babies, which sounds like the cry of a cat
or “le cri du chat” . Alright, our DNA is packaged up into 46 chromosomes,
which contains the genes that are pretty much instructions for making proteins. These proteins control everything from growth
and development to the day-to-day functioning of the cells. Each of the 46 chromosomes is actually made
up of a pair of chromosomes and you get one from each parent, so 23 pairs. Now, these chromosomes are shaped like an
“X” with two short arms and two long arms hooked together in the middle by a centromere. These two short arms are also referred to
as p arms from the French term “petit” that means small. In cri du chat syndrome, a part of one of
the short arms of chromosome 5 is missing and so cri du chat syndrome is also known
as 5p deletion syndrome, or 5p minus. Okay, so 80-85% of the cases of cri du chat
syndrome are the result of de novo deletion, which means they occur on their own without
being inherited. However, in 10% of the cases, the deletion
is inherited from a parent who has a balanced translocation. Translocation means that a part from one chromosome
switches places with a part from another chromosome. and it’s balanced when there is no genetic
material gained or lost, so the person doesn’t experience any adverse affect. As an example, let’s say this woman has
23 pairs of normal chromosomes. And here is her boyfriend, and in his karyotype
we can see that a part of chromosome 5 has switched places with a part of chromosome
11. But he remains normal because no genetic material
is gained or lost. But if these two have a baby, the baby will
randomly inherit 2 copies of each chromosome, one from mom and one from dad. Now since both mom and dad have two copies
of each chromosome, if the dad passes on the translocated chromosome 5, but the normal
chromosome 11, the translocated information from chromosome 5 will be lost. So in this case, the balanced translocation
in the father will become unbalanced translocation in the child because some genetic material
from chromosome 5 is lost and this baby will have cri du chat syndrome. Alright now symptoms of cri du chat syndrome
vary and depend upon the amount of missing genetic material. The most specific feature is obviously the
cat-like cry and it’s due to structural abnormalities of the larynx. Surprisingly, someone can have cri du chat
syndrome without having this characteristic “meowing”. Also, they usually have characteristic facies
with a small, round face with full cheeks, hypertelorism, or increased distance between
the eyes, prominent supraorbital arches, which are the bony ridges above the orbits, and
epicanthal folds, or skin folds of the upper eyelids that cover the inner angles of the
eyes. In addition, the nose is usually flat with
a wide nasal bridge, the ears are low-set, there’s dropped jaw due to increased facial
laxity, and dental malocclusion, or misalignment of the teeth. Besides abnormalities in the head and neck,
It causes congenital heart defects such as ventricular septal defects. There’s also neurological problems including
moderate to severe intellectual disability and slower motor development, leading to delayed
walking and clumsiness. Other common characteristics of babies with
cri du chat syndrome include failure to thrive and hypotonia, or weak muscle tone, which
may become hypertonia later in life. These babies tend to have chronic medical
problems include feeding problems because they have difficulty swallowing, constipation,
and recurrent infections like otitis media, respiratory infections and urinary tract infections. Now, the diagnosis of cri du chat syndrome
can be suspected by the clinical features especially the high-pitched cry. Diagnosis can be confirmed with karyotyping,
which visualizes each chromosome and can be done with a blood test. If there is high clinical suspicion but the
karyotype is negative, fluorescence in situ hybridization, or FISH, can be used. This involves a fluorescently labeled probe
made of DNA that’s complementary to the 5p region. In a normal cell, the probes can base-pair
to both chromosome 5s, so you would expect two bright spots are seen in the microscope
when the cell is viewed under fluorescent light. If a 5p deletion is present, though, one of
those 5p regions is missing, so you’ll only see a single bright spot. Now because cri du chat syndrome is caused
by a genetic deletion, there’s no known cure. So management focuses on maximizing the development
of the affected babies and treating life-threatening conditions, like congenital heart defects. All right as a quick recap, cri du chat syndrome,
or 5p deletion syndrome, is a rare genetic condition where part of the short arm of chromosome
5 is deleted. Cri du chat syndrome is characterized by the
presence of a cat-like cry, but also facial abnormalities and congenital heart defects. Additional findings include failure to thrive,
hypotonia, neurodevelopmental delay, and others. Diagnosis is based on karyotyping to find
the chromosomal abnormalities, and treatment is based on treating life-threatening conditions
after birth.

21 comments

  1. About the unbalanced translocation exemple… Besides the loss of part of chromossome 5, the baby also have a gain in chromosome 11, no? So will it only have cri du chat?

  2. Just so you know, in the beginning of the lecture, you say "26 chromosomes" instead of "46 chromosomes."

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